This specification relates generally to sampling of signals. More particularly, this specification relates to for low power sampling of plethysmograph signals.
Pulse oximeter is an instrument to determine concentration of oxygen in the blood flowing through the peripheral arteries (i.e. arteries that are farthest from the heart). The measure of oxygen in the peripheral arteries is referred to as ‘Saturation of Peripheral Oxygen’ abbreviated as SPO2 and expressed in percentage values. Pulse oximeter determines SPO2 based on a ratio of amount of red (wavelength 600-750 nm) and infrared (wavelength 850-1000 nm) light energy transmitted through (or reflected from) the peripheral arteries. Pulse oximeter enables instantaneous in-vivo measurements of arterial oxygenation as well as heart rate and perfusion signals, and thereby provides an early warning of arterial hypoxemia, for example
Low power consumption is a pre-requisite for portable and wearable medical sensors which allow the subject to move freely. In the case of pulse oximeter, the power consumption is largely due to the power requirement of the light sources (LEDs), which are normally driven continuously at a high rate. Conventional techniques available for reducing the power consumption of the LEDs are based on reduction of the amplitude and/or width of the LED pulses. Further, sampling rates lower than the Nyquist rate of the plethysmograph signal may be employed to reduce the LED power. However, such techniques require additional signal processing tasks such as signal-to-noise ratio measurements and sophisticated reconstruction algorithms which are computationally complex.
There is a need for an enhanced low power sampling of plethysmograph signals.